Olefin disproportionation catalyst and process

ABSTRACT

This present invention relates to a disproportionation catalyst and a process for preparing a disproportionation catalyst comprising forming a calcined composite comprising at least one of molybdenum and rhenium supported on an inorganic oxide support and contacting the calcined composite with an organosilane compound selected from the group consisting of silanes containing at least one silicon-hydrogen bond per molecule, silanes containing at least one silicon-silicon bond per molecule and mixtures thereof, and to a process for the disporportionation of olefinic hydrocarbons comprising contacting at least one olefinic hydrocarbon with a catalyst comprising at least one of molybdenum and rhenium supported on an inorganic oxide support promoted with an organosilane compound selected from the group consisting of silanes containing at least one silicon-hydrogen bond per molecule, silanes containing at least one silicon-silicon bond per molecule and mixtures thereof.

FIELD OF THE INVENTION

This invention relates to a catalyst for use in the disproportionationof olefinic hydrocarbons comprising at least one of molybdenum andrhenium supported on an inorganic oxide support promoted with anorganosilane compound selected from the group consisting of silanescontaining at least one silicon-hydrogen bond per molecule, silanescontaining at least one silicon-silicon bond per molecule and mixturesthereof and a process for the disproportionation of olefinichydrocarbons comprising contacting at least one olefinic hydrocarbonwith a catalyst comprising at least one of molybdenum and rheniumsupported on an inorganic oxide support promoted with an organosilanecompound selected from the group consisting of silanes containing atleast one silicon-hydrogen bond per molecule, silanes containing atleast one silicon-silicon bond per molecule and mixtures thereof.

BACKGROUND OF THE INVENTION

Reactions of olefinic molecules in the presence of metal-containingcatalysts to produce other olefinic molecules are known in the art as"disproportionation" reactions. The olefin disproportionation reactioncan be visualized as the breaking of two existing double bonds betweenthe first and second carbon atoms, and between the third and fourthcarbon atoms, respectively, and the formation of two new double bonds,such as between the first and third carbon atoms and the second andfourth carbon atoms, respectively. A typical olefin disproportionationprocess is illustrated by U.S. Pat. No. 3,261,879, issued Jul. 19, 1966,to Banks, wherein two similar non-symmetrical molecules of an olefinreact in the presence of certain catalysts to produce one olefin of ahigher carbon number and one olefin of a lower carbon number. Forexample, propylene disproportionates by the process of U.S. Pat. No.3,261,879 to produce ethylene and butylenes.

A variation of this disproportionation process, which might be termed"reverse disproportionation" is illustrated by the Netherlands PatentNo. 6514985 of British Petroleum Company, Limited, published May 20,1966, wherein, in one modification, molecules of two dissimilar olefinsare reacted to form two molecules of a single olefin product, e.g..ethylene and 2-butene react to form propylene.

Another variation of this process, being conveniently termed "ringopening disproportionation" to distinguish it from other variations, isdisclosed by Netherlands Patent Application No. 6702703 of PhillipsPetroleum Company, published Aug. 24, 1967, wherein a cyclic olefin andan acyclic olefin react to form a single product molecule. For example,ethylene reacts with cyclopentene by "ring opening disproportionation"to produce 1,6-heptadiene.

As used in this application, "disproportionation process" is meant toinclude all variations of disproportionations.

A variety of catalysts have been employed for conductingdisproportionation reactions, such as those disclosed in U.S. Pat. No.3,340,322, issued Sep. 5, 1967; U.S. Pat. No. 3,637,892, issued Jan. 25,1972; U.S. Pat. No. 3,760,026, issued Sep. 18, 1973; U.S. Pat. No.3,792,108, issued Feb. 12, 1974; U.S. Pat. No. 3,872,180, issued Mar.18, 1975; and British Patent Specification No. 1,128,091, published Mar.16, 1966. Among the catalysts that have been developed fordisproportionation include inorganic refractory materials containingmolybdenum and/or tungsten oxide.

Several patents disclose the use of promoter to enhance thedisproportionation catalyst activity. Elemental metal promoters selectedfrom the group consisting of barium, magnesium, tungsten, silicon,antimony, zinc, manganese and tin are disclosed in U.S. Pat. No.4,568,788, issued Feb. 4, 1986, U.S. Pat. No. 4,522,936, issued Jun. 11,1985, U.S. Pat. No. 4,524,235, issued Jun. 18, 1985 and U.S. Pat. No.4,629,719, issued Dec. 16, 1986. In addition. organometallic compounds,such as aluminum and tin alkyls to promote solid catalysts includingmolybdenum and rhenium oxide for the disproportionation are disclosed inU.S. Pat. No. 4,454,368, issued Jun. 12, 1984 and U.S. Pat. No.3,829,523, issued Aug. 13, 1974.

It is an object of this invention to provide a catalyst system withnovel promoters for olefin disproportionation at high activity.

The present invention is therefore directed to a method of improving theactivity of a disproportionation catalyst for converting olefins intoolefins having different numbers of carbon atoms than the feed olefinichydrocarbons.

SUMMARY OF THE INVENTION

This present invention relates to a disproportionation catalystcomprising at least one of molybdenum and rhenium supported on aninorganic oxide support promoted with an organosilane compound selectedfrom the group consisting of silanes containing at least onesilicon-hydrogen bond per molecule, silanes containing at least onesilicon-silicon bond per molecule and mixtures thereof and to a processfor preparing a disproportionation catalyst comprising forming acalcined composite comprising at least one of molybdenum and rheniumsupported on an inorganic oxide support and contacting the calcinedcomposite with an organosilane compound selected from the groupconsisting of silanes containing at least one silicon-hydrogen bond permolecule, silanes containing at least one silicon-silicon bond permolecule and mixtures thereof. The invention further relates to aprocess for the disproportionation of olefinic hydrocarbons comprisingcontacting at least one olefinic hydrocarbon with a catalyst comprisingat least one of molybdenum and rhenium supported on an inorganic oxidesupport promoted with an organosilane compound selected from the groupconsisting of silanes containing at least one silicon-hydrogen bond permolecule, silanes containing at least one silicon-silicon bond permolecule and mixtures thereof.

It has been found that the activity of a disproportionation catalyst canbe improved by contacting the catalyst with an organosilane compoundselected from the group consisting of silanes containing at least onesilicon-hydrogen bond per molecule, silanes containing at least onesilicon-silicon bond per molecule and mixtures thereof, under conditionssuitable for the organosilane compound to promote the activity ofmolybdenum and rhenium oxides. The activity of the disproportionationcatalyst can be enhanced up to several orders of magnitude rate increaseby the presence of an organosilane compound thus enabling thedisproportionation reaction to be carried out at ambient temperaturewith advantages of high reaction productivity and product selectivity.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the process of the instant invention, the disproportionation of anolefinic hydrocarbon is accomplished by contacting one or more olefinichydrocarbons with a disproportionation catalyst comprising at least oneof molybdenum and rhenium supported on an inorganic oxide support in thepresence of an organosilane promoter selected from the group consistingof silanes containing at least one silicon-hydrogen bond per molecule,silanes containing at least one silicon-silicon bond per molecule andmixtures thereof.

Olefins which are suitable for disproportionation according to theinstant invention are nontertiary, nonconjugated acyclic monoolefins andpolyolefins having at least 2 carbon atoms per molecule includingcycloalkyl, cycloalkenyl and aryl derivatives thereof; cyclic andpolycyclic monoolefins and polyolefins having at least 3 carbon atomsper molecule including alkyl and aryl derivatives thereof; mixtures ofthe above olefins; and mixtures of ethylene and the above olefins. Auseful group of olefin feed materials are acyclic olefins having carbonnumbers ranging from C₂ to about C₅₀, preferably from C₃ to about C₃₀,and cyclic olefins having carbon numbers ranging from C₄ to about C₃₀.Nontertiary olefins are those olefins wherein each carbon atom, which isattached to another carbon number by means of a double bond, is alsoattached to at least one hydrogen atom.

Some specific examples of acyclic olefins suitable fordisproportionation according to this invention are acyclic 1- and2-alkenes, and alkyl and aryl derivatives thereof having from 2 to 30carbon atoms per molecule. Some specific examples of such olefins arepropylene, 1-butene, 2-butene, 1-pentene, 2-pentene, 1-hexene,2-heptene, 1-octene, 2-nonene, 1-dodecene, 2-tetradecene, 1-hexadecene,2-methyl-1-butene, 2-methyl-2-butene, 3-methyl-1-butene,1-phenylbutene-2, 3-heptene and the like, and mixtures thereof.

Some specific examples of cyclic olefins suitable for disproportionationaccording to this invention are cyclobutene, cyclopentene, cycloheptene,cyclooctene, 5-n-propylcyclooctene, cyclodecene, cyclododecene,3,3,5,5-tetramethylcyclononene, 3,4,5,6,7-pentaethylcyclodecene,1,5-cyclooctadiene, 1,5,9-cyclododecatriene,1,4,7,10-cyclododecatetraene, 6-methyl-6-ethylcyclooctadiene-1,4 and thelike, and mixtures thereof.

The olefin feed should be essentially free of impurities which adverselyaffect the reaction. A subsequent reactivation of the catalyst to removethe effect of such impurities can be made repeatedly by heat treatmentwith air, using an inert gas to control burn-off temperature.

The disproportionation catalyst in the instant invention is prepared byforming a calcined composite comprising at least one of molybdenum andrhenium supported on an inorganic oxide support and contacting thecalcined composite with a promoting amount of an organosilane compound.The inorganic oxide support comprises a solid usually containing a majorproportion of silica or alumina. Such materials are commonly known asrefractory oxides and include synthetic products as well as acid-treatedclays or the crystalline alumina silicates known in the art as molecularsieves. Synthetic refractory oxides include silica, alumina.silica-alumina, silica-magnesia, silica-titania, alumina-titania,alumina-magnesia, boria-alumina-silica, alumina-zirconia, thoria andsilica-titania-zirconia. Preferred inorganic oxide supports are aluminarefractory oxides, i.e., refractory oxides containing a substantialproportion of alumina, e.g., at least about 90 percent by weight ofalumina. Any conventional catalytic grade of alumina including the betaor gamma forms can be used. Generally, the inorganic oxide support has asurface area of at least 10 m² /g and preferably, the surface area isfrom about 25 m² /g to 800 m² /g.

The molybdenum and/or rhenium can be combined with the inorganic oxidesupport in any conventional method such as dry mixing, ion-exchange.coprecipitation, impregnation and the like. For example, a 10-100 meshalumina can be impregnated with an aqueous solution containingmolybdenum salts, such as ammonium heptamolybdate or ammoniumdimolybdate.

In a preferred embodiment, the disproportionation catalyst in theinstant invention is a molybdenum oxide prepared by impregnating aluminawith an aqueous molybdenum impregnation solution. The aqueous molybdenumsolution consists of a water-soluble source of molybdenum oxide such asammonium heptamolybdate or ammonium dimolybdate dissolved in water.Hydrogen peroxide may also be used to aid in solution preparation insome cases. For example, the molybdenum solution can be prepared byadding hydrogen peroxide to the solution in an amount in the range offrom about 0.1 to about 1.0 mole of hydrogen peroxide per mole ofmolybdenum. Optionally, a suitable soluble amine compound such asmonoethanolamine, propanolamine or ethylenediamine may be added to themolybdenum solution in order to aid in stabilization of the solution.

Following impregnation, the resulting material is dried and calcined.Drying is accomplished by conventional means. It may be carried out byforced draft drying, vacuum drying, air drying or similar means. Dryingtemperatures are not critical and depend upon the particular meansutilized for drying. Drying temperatures will typically range from about50° C. to about 150° C.

After drying, the material is calcined to produce the finished catalyst.The material may be calcined in an oxidizing or neutral atmosphere,although air is preferred. However, if binders and/or lubricants areused the material is heated in an oxygen-containing atmosphere,preferably air, in order to burn out the binders and lubricants.Calcining temperatures will typically range from about 300° C. to about600° C. Burn-out temperatures will depend on the concentration of oxygenin the burn-out atmosphere as well as the burn-out time involved.Typically, burn-out temperatures will range from about 300° C. to about600° C. Drying, calcining and burn-out may be combined in one or twosteps. Most frequently the calcining and/or burn-out steps are combinedusing an oxygen-containing atmosphere.

The final calcined composites typically contain from about 1 percent byweight to about 18 percent by weight, preferably from about 5 percent byweight to about 15 percent by weight, and more preferably from about 6percent by weight to about 12 percent by weight molybdenum and fromabout 1 percent by weight to about 20 percent by weight, preferably fromabout 5 percent by weight to about 15 percent by weight. and morepreferably from about 6 percent to about 12 percent by weight rhenium.When mixtures of molybdenum and rhenium are utilized, the final catalysttypically contains from about 1 percent by weight to about 32 percent byweight molybdenum and rhenium. These types of catalysts are well knownin the art and reference can be prepared according to the prior art,such as but not limited to aforementioned U.S. Pat. No. 3,261,879 andU.S. Pat. No. 3,365,513 (both of which are incorporated by referenceherein) for more specific details about these types of catalysts.

The supported molybdenum and/or rhenium oxide composites are preferablysubjected to a pretreatment prior to contact with the organosilanecompound which is selected from the group consisting of silanescontaining at least one silicon-hydrogen bond per molecule, silanescontaining at least one silicon-silicon bond per molecule and mixturesthereof. While pretreatment is usually accomplished by contacting thecatalyst with an oxygen-containing gas at elevated temperatures, otheractivation methods such as heating under a vacuum, or contact withvarious gases such as nitrogen or argon at high temperatures can beused. One function served by this type of pretreatment is to convert themolybdenum and/or rhenium components into the form of the oxide if thesecomponents are not initially provided in these forms. The temperature,contact times, and other conditions of pretreatment have been reportedin the prior art and are generally the same conditions which areutilized to activate a disproportionation catalyst. Typically. thepretreatment conditions include a temperature in the range of from about300° C. to about 900° C. for about 30 minutes to about 24 hours.

In order to obtain the active catalyst composition of the instantinvention, the molybdenum and/or rhenium oxide supported composition istreated with an organosilane compound selected from the group consistingof silanes containing at least one silicon-hydrogen bond per molecule,silanes containing at least one silicon-silicon bond per molecule andmixtures thereof. The promoting organosilane compound can be combinedwith the molybdenum or rhenium oxide supported compositions in anysuitable manner. For example, the molybdenum and/or rhenium oxidesupported composition can be impregnated with a liquid diluentcontaining the organosilane compound at ambient temperature up to 150°C. After impregnation, the catalyst is then heated in an inertatmosphere, such as nitrogen or argon, to remove the liquid diluent. Thetemperature employed in removing the diluent and activating can varywidely; however, temperatures in the range of about 25° C. to about 200°C. are preferred. If desired, the organosilane promoter can be appliedto the supported molybdenum and/or rhenium oxide in a reaction zone byspraying or otherwise contacting with the oxide. It is also contemplatedthat the organosilane promoter can be introduced along with the olefinfeed as a means for contacting with supported molybdenum and/or rheniumoxide. In a preferred embodiment, the organosilane promoter is contactedwith the supported molybdenum and/or rhenium oxide before contact withthe olefin feed.

In accordance with the invention, the calcined molybdenum and/or rheniumoxide refractory materials are treated with an effective promotingamount of an organosilane compound selected from the group consisting ofsilanes containing at least one silicon-hydrogen bond per molecule,silanes containing at least one silicon-silicon bond per molecule andmixtures thereof and heated under conditions to form a promotedcatalyst. Suitable organosilane promoters having at least onesilicon-hydrogen bond per molecule include trialkylsilanes such astriethylsilane, tricyclohexylsilane, trimethylsilane, tripropylsilane,tri-n-butylsilane and tri-n-hexylsilane; mixed trialkylsilanes such asmethyldiethylsilane and dimethylethylesilane; dialkylsilanes such asdiethylsilane and dimethylsilane., arylsilanes such as triphenylsilane,diphenylsilane; and alkoxysilanes such as triethoxysilane. The preferredorganosilane compounds having at least one silicon-hydrogen bond permolecule are trialkylsilanes such as triethylsilane, diphenylsilane,triphenylsilane, tri-n-butylsilane, and the like, with triethylsilaneand diphenylsilane being especially preferred. Suitable organosilanepromoters having at least one silicon-silicon bond per molecule includedisilanes such as hexamethyldisilane, hexaethyldisilane andhexabutyldisilane. The preferred organosilanes having at least onesilicon-silicon bond per molecule are hexamethyldislane,hexaethyldisilane, trimethyltriethyldisilane, hexaphenyldisilane and thelike, with hexamethyldisilane and hexaethyldisilane being especiallypreferred. In a preferred embodiment, the organosilane promoter in theinstant invention is a dialkyl or trialkylsilane, preferablytriethylsilane, tri-n-butylsilane or diphenylsilane. Suitable molybdenumor rhenium oxide/organosilane molar ratios are typically in the range offrom about 0.1 to about 500, preferably from about 1 to about 200. morepreferably, from about 2 to about 100, and most preferably, from about 5to about 50.

The disproportionation process of the invention can be carried outeither batchwise or continuously, using a fixed catalyst bed, or astirrer equipped reactor or other mobile catalyst contacting process aswell as any other well known contacting technique. Preferred reactionconditions, e.g., temperature, pressure, flow rates, etc., vary somewhatdepending upon the specific catalyst composition, the particular feedolefin, desired products, etc. The process is carried out attemperatures ranging from about -10° C. to about 350° C. and atpressures in the range of about 50 psig to about 2000 psig. Thedisproportionation reaction is usually effected in a liquid phase and ifdesired, liquid reaction diluents are utilized. Examples of suitablediluents are hydrocarbons free from aliphatic unsaturation, such asacyclic or alicyclic alkanes of from 6 to 12 carbon atoms, i.e. hexane,isooctane and cyclohexane. Also exemplary are monoaromatic compoundssuch as benzene and toluene. If the diluent is added, it is present inamounts up to 20 moles of diluent per mole of olefinic reactants.

The operable range of contact time for the process of this inventiondepends primarily upon the operating temperature and the activity of thecatalyst, which is influenced by surface area, promoter concentration,activation temperature, etc. In general, the distribution of products isnot drastically altered by variation in contact time. Shorter contacttimes are usually associated with higher temperatures. With properselection of conditions and contact times, very high efficiency ofconversion to desired products can be obtained.

With a fixed bed reactor, continuous flow operation at pressures in therange of about 50 psig to about 2000 psig, preferably about 100 psig toabout 1000 psig, with catalysts having densities ranging from about 0.3gram per cc to about 2.0 gram per cc and surface areas greater thanabout 100 m² /g, and at temperatures in the range of about -10° C. toabout 350° C., preferably at room temperature, weight hourly spacevelocities in the range of about 0.1 to about 10.0 parts by weight ofolefinic hydrocarbon feed per part by weight of catalyst per hour aresuitable. The space velocity is adjusted according to changes in densityof feed due to change of pressure or temperature. and variation inreaction temperature and the activity of the catalyst.

The ranges and limitations provided in the instant specification andclaims are those which are believed to particularly point out anddistinctly claim the instant invention. It is, however, understood thatother ranges and limitations that perform substantially the samefunction in substantially the same manner to obtain the same result areintended to be within the scope of the instant invention as defined bythe instant specification and claims.

The process of the instant invention will be further described below bythe following examples which are illustrative and which are not to beconstrued as limiting the invention.

ILLUSTRATIVE EMBODIMENTS Catalyst Preparation

The disproportionation catalyst was prepared using a conventional drypore volume impregnation technique.

A 12% MoO₃ /Al₂ O₃ catalyst was prepared as follows. A solution suitablefor impregnating 88 grams of calcined alumina support with a pore volumeof 1.0 cm/g was prepared as follows. An impregnation solution was madeby combining 14.7 grams of ammonium heptamolybdate, 5.7 grams of 30%hydrogen peroxide and 32.4 grams of deionized water or enough water tobring the solution to a total volume of 88 milliliters. After adding theentire solution to the alumina support in several small portions withintermediate agitations, the impregnated support was dried overnight at150° C. and calcined in air for at least 2 hours at 550° C. and innitrogen for at least 1 hour 550° C.

A 6% MoO₃ Al₂ O₃ catalyst was prepared as follows. A solution suitablefor impregnating 88 grams of calcined alumina support with a pore volumeof 1.0 cm/g was prepared as follows. An impregnation solution was madeby combining 7.4 grams of ammonium heptamolybdate, 2.9 grams of 30%hydrogen peroxide and 16.2 grams of deionized water or enough water tobring the solution to a total volume of 44 milliliters. After adding theentire solution to the alumina support in several small portions withintermediate agitations, the impregnated support was dried overnight at150° C and calcined in air for at least 2 hours at 550° C. and innitrogen for at least 1 hour at 550° C.

DISPROPORTIONATION OF 1-DECENE EXAMPLE 1

To a 50 ml oven-dried round bottomed flask equipped with a magnetic stirbar and a three-way stopcock was added 12% molybdenum oxide on aluminacatalyst (2.0 g, 1.7 mmoles MoO₃), 1-decene (20 mol, 105 mmoles) andtriethylsilane (0.02 g, 0.17 mmoles) under nitrogen atmosphere. Themixture was then stirred at room temperature. Periodically, samples weretaken and analyzed by glc. The products were further identified bygc-mass spectrometry and other analytic means. This example demonstrateshigh catalyst activity at room temperature for 1-decenedisproportionation to C₁₈ olefins. The results of the disproportionationreaction are presented in Table I.

EXAMPLE 2

The disproportionation was carried out in the same manner as Example 1except that diphenylsilane (0.008 g, 0.043 mmoles) was used in place oftriethylsilane as promoter. The results of the disproportionationreaction are presented in Table I.

EXAMPLE 3

The disproportionation was carried out in the same manner as Example 1except that diphenylsilane (0.004 g, 0.021 mmoles) was used in place oftriethylsilane as promoter. The results of the disproportionationreaction are presented in Table I.

COMPARATIVE EXAMPLE A

The disproportionation was carried out in the same manner as Example 1except that no promoter was present. The results of thedisproportionation reaction are presented in Table I.

EXAMPLE 4

To a 50 ml oven-dried round bottomed flask equipped with a magnetic stirbar and a three-way stopcock was added 6% molybdenum oxide on aluminacatalyst (2.0 g, 0.9 mmole MoO₃), 1-decene (20 mol, 105 mmoles) anddiphenylsilane (0.032 g. 0.17 mmole) under nitrogen atmosphere. Themixture was then stirred at room temperature. Periodically, samples weretaken and analyzed by glc. The products were further identified bygc-mass spectrometry and other analytic means. This example demonstrateshigh catalyst activity at room temperature for 1-decenedisproportionation to C₁₈ olefins. The results of the disproportionationreaction are presented in Table I.

COMPARATIVE EXAMPLE B

The disproportionation was carried out in the same manner as Example 4except that no promoter was present. The results of thedisproportionation reaction are presented in Table I.

                                      TABLE I                                     __________________________________________________________________________    DISPROPORTIONATION OF 1-DECENE                                                                       Reaction                                                                           Olefin Product Mixtures %                                         Silane Added                                                                         Time Unreacted                                                Catalyst (Mmoles)                                                                             (hr) Decenes                                                                            C.sub.16.sup.=                                                                    C.sub.17.sup.=                                                                    C.sub.18.sup.=                       __________________________________________________________________________    Example 1                                                                            12% MoO.sub.3 /Al.sub.2 O.sub.3                                                        Et.sub.3 SiH                                                                         3    76   0   1   19                                                   (0.17) 18   43   0   2   48                                   Example 2                                                                            12% MoO.sub.3 /Al.sub.2 O.sub.3                                                        Ph.sub.2 SiH.sub.2                                                                   3    67   0   2   26                                                   (0.043)                                                                              18   22   2   11  48                                   Example 3                                                                            12% MoO.sub.3 /Al.sub.2 O.sub.3                                                        Ph.sub.2 SiH.sub.2                                                                   3    70   0   2   23                                                   (0.021)                                                                              18   21   2   11  49                                   Comparative                                                                          12% MoO.sub.3 /Al.sub.2 O.sub.3                                                        None   3    79   0   0    3                                   Example A                                                                     Example 4                                                                             6% MoO.sub.3 /Al.sub.2 O.sub.3                                                        Ph.sub.2 SiH.sub.2                                                                   3    79   0   1   17                                                   (0.17) 18   24   3   6   56                                   Comparative                                                                           6% MoO.sub.3 /Al.sub.2 O.sub.3                                                        None   3    93   0   0    1                                   Example B                                                                     __________________________________________________________________________

I claim as my invention:
 1. A disproportionation catalyst comprising atleast one of molybdenum and rhenium supported on an inorganic oxidesupport promoted with an organosilane compound selected from the groupconsisting of silanes containing at least one silicon-hydrogen bond permolecule, silanes containing at least one silicon-silicon bond permolecule and mixtures thereof, wherein said organoxilane compoundcontaining at least one silicon-hydrogen bond per molecule is selectedfrom the group consisting of triethylsilane, tricyclohexylsilane,trimethylsilane, diethylsilane, diphenylsilane, triphenylsilane, andmixtures thereof, and wherein said organosilane compound containing atleast one silicon-silicon bond per molecule is selected from the groupconsisting of hexamethyldisilane, hexaethyldisilane,trimethyltriethyldisilane, hexaphenyldisilane, and mixtures thereof. 2.The catalyst of claim 1 wherein said organosilane compound is selectedfrom triethylsilane and diphenylsilane.
 3. The catalyst of claim 1wherein said organosilane compound is selected from hexamethyldisilaneand hexaethyldisilane.
 4. The catalyst of claim 1 wherein the molybdenumand/or rhenium/organosilane molar ratio is in the range of from about0.1 to about
 500. 5. The catalyst of claim 4 wherein the molybdenumand/or rhenium/organosilane molar ratio is in the range of from about 1to about
 200. 6. The catalyst of claim 5 wherein the molybdenum and/orrhenium/organosilane molar ratio is in the range of from about 5 toabout
 50. 7. The catalyst of claim 1 wherein said disproportionationcatalyst contains from about 1 percent by weight to about 18 percent byweight molybdenum.
 8. The catalyst of claim 7 wherein saiddisproportionation catalyst contains from about 5 percent by weight toabout 15 percent by weight molybdenum.
 9. The catalyst of claim 8wherein said disproportionation catalyst contains from about 6 percentby weight to about 12 percent by weight molybdenum.
 10. The catalyst ofclaim 1 wherein said disproportionation catalyst contains from about 1percent by weight to about 20 percent by weight rhenium.
 11. Thecatalyst of claim 10 wherein said disproportionation catalyst containsfrom about 5 percent by weight to about 15 percent by weight rhenium.12. The catalyst of claim 11 wherein said disproportionation catalystcontains from about 6 percent by weight to about 12 percent by weightrhenium.
 13. The catalyst of claim 1 wherein said inorganic oxidesupport is selected from the group consisting of silica, alumina,silica-alumina, silica-magnesia, silica-titania, alumina-titania,alumina-magnesia. boria-alumina-silica, alumina-zirconia, thoria,silica-titania-zirconia and mixtures thereof.
 14. The catalyst of claim13 wherein said inorganic oxide support is alumina.
 15. A process forpreparing a disproportionation catalyst comprising forming a calcinedcomposite comprising at least one of molybdenum and rhenium supported onan inorganic oxide support and contacting the calcined composite with anorganosilane compound selected from the group consisting of silanescontaining at least one silicon-hydrogen bond, silanes containing atleast one silicon-silicon bond per molecule and mixtures thereof,wherein said organosilane compound containing at least onesilicon-hydrogen bond per molecule is selected from the group consistingof triethylsilane, tricyclohexylsilane, trimethylsilane, diethylsilane,diphenylsilane, triphenylsilane, and mixtures thereof, and wherein saidorganosilane compound containing at least one silicon-silicon bond permolecule is selected from the group consisting of hexamethyldisilane,hexaethyldisilane, trimethyltriethyldisilane, hexaphenyldisilane, andmixtures thereof.
 16. The process of claim 15 wherein said organosilanecompound is selected from triethylsilane and diphenylsilane.
 17. Theprocess of claim 15 wherein said organosilane compound is selected fromhexamethyldisilane and hexaethyldisilane.
 18. The process of claim 15wherein the molybdenum and/or rhenium/organosilane molar ratio is in therange of from about 0.1 to about
 500. 19. The process of claim 18wherein the molybdenum and/or rhenium/organosilane molar ratio is in therange of from about 1 to about
 200. 20. The process of claim 19 whereinthe molybdenum and/or rhenium/organosilane molar ratio is in the rangeof from about 5 to about
 50. 21. The process of claim 15 wherein saiddisproportionation catalyst contains from about 1 percent by weight toabout 18 percent by weight molybdenum.
 22. The process of claim 21wherein said disproportionation catalyst contains from about 5 percentby weight to about 15 percent by weight molybdenum.
 23. The process ofclaim 22 wherein said disproportionation catalyst contains from about 6percent by weight to about 12 percent by weight molybdenum.
 24. Theprocess of claim 15 wherein said disproportionation catalyst containsfrom about 1 percent by weight to about 20 percent by weight rhenium.25. The process of claim 24 wherein said disproportionation catalystcontains from about 5 percent by weight to about 15 percent by weightrhenium.
 26. The process of claim 25 wherein said disproportionationcatalyst contains from about 6 percent by weight to about 12 percent byweight rhenium.
 27. The process of claim 15 wherein said inorganic oxidesupport is selected from the group consisting of silica, alumina,silica-alumina, silica-magnesia, silica-titania, alumina-titania,alumina-magnesia, boria-alumina-silica, alumina-zirconia, thoria,silica-titania-zirconia and mixtures thereof.
 28. The process of claim27 wherein said inorganic oxide support is alumina.
 29. The process ofclaim 15 wherein said composite is calcined by activating with anoxygen-containing gas at a temperature of from about 300° C. to about800° C. prior to the addition of the organosilane promoter.